The invention relates to a supporting disk for a supporting disk bearing for a shaft of an open-end spinning rotor.
Supporting disk bearings are used very successfully and in large numbers in open-end rotor spinning machines. The continuing rise of the rotational speeds results in problems, such as increased wear at rings of the supporting disks that are made of plastic. Such disks include a metal base body which is surrounded by a plastic ring. It was found that the rings heat up in a center area and thus a heat build-up occurs in this area, particularly at high rotational speeds. At times, bubbles form directly under the surface of the rings. In some cases, these bubbles later opened up, and plastic material has broken out at various points. These crater-type holes resulted in the spinning rotor no longer running smoothly, so that the rotor shaft delivered hard blows to the running surface. This accelerated the damaging of the plastic rings. It is assumed that the heating-up in the rings made of plastic results because the rotor shaft causes only a slight deformation at the plastic rings which is connected with a flexing process.
In German Published Unexamined Patent 3,447,600, a surrounding ring groove is provided in the center of the running surfaces which improves the dissipation of heat in the central area. In this patent, the depth of the ring groove is selected such that it corresponds to approximately half the thickness of the plastic ring in radial direction. This arrangement merely increases air flow through the ring groove to dissipate heat, and does not address reducing the stress in the central running surfaces of the disk.
It has also been suggested in Patent Application P 36 15 777.5, which is not a prior publication and thus is not prior art, to provide the plastic rings with an uninterrupted cylindrical running surface, and to achieve a reduction of the heating-up process by providing a profiling of the base body which engages in the inner surface of the ring. The profiling reduces the thickness of the central area of the rings in comparison to the edge areas on either side of the central area. By reducing the thickness of the central area, the build-up of heat is reduced in this area, while, at the same time, the heat dissipation via the base body is improved.
An object of the present invention is to provide a further improvement of a supporting disk assembly of the initially mentioned type in view of possible heating-up and the resulting wear phenomenon.
This object and other objects are achieved by providing an outer circumferential area of a supporting disk with a ring groove having a depth in radial direction slightly larger than the elastic deformation of the running surface in radial direction caused by the rotor shaft.
In the present invention, the shaft just barely does not come in contact with the outer surface of the supporting disk in the area of the ring groove. Because of the shallow depth, the ring groove is very flat. The very flat ring groove is not created to merely improve the cooling air flow through the ring groove, and thus to improve the dissipation of heat that is shown in known arrangements. The very flat ring groove according to the present invention provides a reduction of stress in the supporting disk, caused by the shaft of the spinning rotor such that the stress is removed from the running surfaces in the central area. Therefore, the rotor shaft does not subject the supporting disk to any flexing process in the central area.
According to advantageous features of certain preferred embodiments of the invention, the outer circumferential area of the supporting disk includes a ring made of plastic. The very low depth of the ring groove also has the advantage that the plastic ring is practically not weakened in axial direction. In this case, it should be noted that via the plastic rings of the supporting disks, an axial force is exercised on the shaft of the spinning rotor against which the shaft is supported at the step bearing. A deep ring groove may have the effect that the ring is weakened as the result of a type of "notch effect".
In other advantageous features of certain preferred embodiments of the invention, a profiling (or flange) is provided between the circumference of the base body and the inner surface of the ring. This results not only in a good connection between the base body and the ring, but because the contact surfaces are enlarged, the dissipation of heat via the metallic base body is also improved. In certain embodiments, it is provided in this case that the profiling is constructed as a ring groove and a rib and is arranged essentially symmetrically with respect to the radial center plane of the ring. As a result, it is achieved that the ring in the center has only a relatively low accumulation of material so that the danger of a build-up of heat in the central area is reduced further.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.